D3 A8 4.2 sport. ~160k on the clock. Got it a couple of years back from a ultra crappy dealer. It had been auctioned and the paperwork isn't the best. Theres a book with some bits in it but I don't recall anything about gearbox servicing. It's a daily driver rather than a show car and it's done pretty well over the last two years.

The other day i got an error, limp mode, thud etc. I was rushing and doing a quick three point turn and it was going quickly into reverse.
Car off and on and everything normal.

Then i did something similar a few days later after a low battery (indicator overnight) and the key was in the ignition and i couldn't turn it off and on for fear on having just started it.....So i popped my ODB11 bluetooth dongle in and and cleared the transmission error and the car was fine again.

I also had a thing where i pulled away and the gear stuck, the revs hit high and limp mode. That flagged a different error (revs) and incorrect on gear 4!

The gearbox has been a bit lumpy recently too (high power shifts) and i've notice a whine/noise when under power going round corners. Driving gently and it seems fine. Motorway stuff and it's great. It seems more prone to be lumpy/hesitant when starting off.....once it's warmed it's much better.

I'm wondering if the gearbox fluid is low, needs a change or something ???

I should probably get my VCDS stuff out and have a look too!

I'm Peterborough / Cambridgeshire if anyone knows of a recommendation?

The early ones are. The later ones like the FBG in your 2002 seem to be more affected by the A-drum roller bearing collapsing which then causes the clutch pack to slip and shreds an o-ring which releases line pressure causing all the other clutches to also slip.

Changing the valve body is simple if you are meticulous about detail and cleanliness although its a very messy job in the car since it holds a lot of oil which will drop on you I would argue though that if its shifting ok then changing it is a waste of money. The best preventive maintenance on it is to change the bearing, but that's inside the box behind the oil pump so is a considerably bigger job. Still, its pretty obvious when that bearing has failed (clutches slipping) and if you get to it immediately it won't do any lasting damage.

MikkiJayne - I know you posted this in relation to a D2 and a valve body but I'm wondering if this sort of thing is happening on my D3 ???

I've had the error on multiple gear ratios which would indicate something related - Curiously whilst driving this morning, I put it in 4th for a bit and i got fluctuating revs and even lurchy type behavior whilst in one gear!

I think first thing I would do is check level when engine warm , get a sample of the oil and smell it ....see if it smells of burnt toast .

In correct ratio codes ,or codes like input shaft speed incoherence to output speed very often signs of slipping clutch packs , bumping through the gears ‘flare up ‘ symptoms aswell ...... low oil levels can cause similar issues but it does have to be quite low for this ...any oil leaks seen ??

Dropped the gearbox pan. Oil dark and grimy but didn't smell toasty, just ATF'y. Evidence of leaks around the gasket and possibly the seal round the prop shaft.
The pan magnets didn't seem to have any obvious metal deposits, but were slimy.
New filter, gasket, bolts and seals from a Meyle kit as it seems the filter on my gearbox isn't the standard one.
Took a lot more oil to fill than was removed, going through the gears at the right temp etc.

Initial test drive and taking it out of my work estate and onto the main road and i was already in 3rd before I realised it had even shifted and that was by knocking it into manual. Power delivery is immediate and no sounds from third or fourth going round corners under power. Definitely different.

Drove home last night and back again and it's a different car. Most the time you can hardly tell the gears are changing apart from the rev counter. The revs stay solid when you are at a constant on the gas pedal (they fluctuated before) and having a quick play with kick down, Manual mode, 6th gear, floored it and it dropped to 3rd and speed just happened. Surprisingly smooth and effortless.

The gearbox feels smoother and better than I recall it when buying two years ago. Power is just THERE on tap. Quite a different car!

I've only done ~25 miles and I want a few hundred to say it's properly worked, but so far things are VERY promising

Dropped the gearbox pan. Oil dark and grimy but didn't smell toasty, just ATF'y. Evidence of leaks around the gasket and possibly the seal round the prop shaft.
The pan magnets didn't seem to have any obvious metal deposits, but were slimy.
New filter, gasket, bolts and seals from a Meyle kit as it seems the filter on my gearbox isn't the standard one.
Took a lot more oil to fill than was removed, going through the gears at the right temp etc.

Initial test drive and taking it out of my work estate and onto the main road and i was already in 3rd before I realised it had even shifted and that was by knocking it into manual. Power delivery is immediate and no sounds from third or fourth going round corners under power. Definitely different.

Drove home last night and back again and it's a different car. Most the time you can hardly tell the gears are changing apart from the rev counter. The revs stay solid when you are at a constant on the gas pedal (they fluctuated before) and having a quick play with kick down, Manual mode, 6th gear, floored it and it dropped to 3rd and speed just happened. Surprisingly smooth and effortless.

The gearbox feels smoother and better than I recall it when buying two years ago. Power is just THERE on tap. Quite a different car!

I've only done ~25 miles and I want a few hundred to say it's properly worked, but so far things are VERY promising

Which kit did you use? How many litres did it take? Also hopefully is sorted now.